DESCRIPTION: (Applicant's Description) The natural history of breast cancer is complex, requiring that treatment modalities be adjusted to the stage and heterogeneity of the disease. The type of treatment and the prognosis of a breast cancer patient have been up to now established on the basis of certain prognostic indicators, such as extent of axillary nodal metastasis, and the size, histological type, steroid hormone receptor content and cell proliferation index of the primary tumor. More recently the detection of oncogenes, tumor suppressor genes, loss of heterozygosity, and growth factors have emerged as potential indicators of tumor behavior. The evaluation of the prognostic significance of new tumor markers, however, has been hindered by a lack of adequate number of breast cancer cases for achieving statistical significance of endpoints, as well as by the lack of adequate patient information and follow-up, lack of uniformity in the therapeutic modalities utilized, and poor computerization systems for the retrieval of the desired cases for performing these studies. These needs have been addressed by the National Cancer Institute (NCI) through the creation of the Cooperative Breast Tissue Resource (NCI-CBCTR) of which the Fox Chase Cancer Center Breast Cancer Tissue Resource (FCCC-BCTR) is an integral part. The main goal of this resource was to create a repository of archival breast tissue that would be made available to researchers interested in testing and validating new tumor markers. The FCCC-BCTR has been one of the four pillars on which the NCI-CBCTR was created, contributing more than 2,800 cases to the total of 7,600 cases entered in the NCI-CBCTR database during the last four years. These cases count with the archival paraffin tissue, data on demography, pathology, clinical stage, treatment, and patient follow-up. Based on this contribution we propose the maintenance of the FCCC BCTR as part of the NCI-CBCTR by fulfilling the following specific aims: to cooperate with the members of the NCI-CBCTR for expeditiously delivering tissue sections and pertinent clinical data to investigators whose applications have been recommended for approval by merit and content by the Research Evaluation Panel (REP) and approved by the NCI-CBCTR; to maintain an adequate quality control of tissue blocks, sections, and clinical data; to fully participate in the functioning of the Coordinating Committee and to collaborate with the REP of the NCI-CBCTR; to encourage the utilization of this resource through an adequate marketing initiative; and to maintain an adequate accrual of new cases for replenishing those archival cases exhausted by continuous usage. This last specific objective will be implemented at the end of two years of functioning, after assessing the number and type of tissues that remain in the resource and the number and type of tissues and cases requested in new applications that are expected to be fulfilled during the ensuing three years. The FCCC-BCTR, together with NCI staff will then determine the need, if any, to expand the resource with new specimens of breast cancer or to modify its structure and/or function.